Field of the Invention
The present invention relates to an apparatus for suppressing fuel evaporative gas emission, and more particularly to control for detecting an abnormality of the apparatus for suppressing fuel evaporative gas emission.
Description of the Related Art
Conventionally, in order to prevent emission of a fuel evaporative gas evaporated in a fuel tank into the atmosphere, an apparatus for suppressing fuel evaporative gas emission is provided including: a canister mounted in a purge passage that provides communication between a fuel tank and an intake passage of an internal combustion engine; a changeover valve that opens or closes the canister to or from the atmosphere; a sealing valve that provides communication or closes between the fuel tank and the canister; and a purge solenoid valve that provides communication of and interrupts the purge passage. The apparatus for suppressing fuel evaporative gas emission opens the changeover valve and the sealing valve and closes the purge solenoid in fueling so that the fuel evaporative gas flows toward the canister, and the fuel evaporative gas is adsorbed to activated carbon provided in the canister. The apparatus for suppressing fuel evaporative gas emission opens the changeover valve and the purge solenoid valve in operation of the internal combustion engine, and discharges the fuel evaporative gas adsorbed to the activated carbon in the canister to the intake passage of the internal combustion engine to treat the fuel evaporative gas. The apparatus for suppressing fuel evaporative gas emission also detects a leak from the apparatus in order to prevent the fuel evaporative gas from leaking outside the apparatus.
For leak detection, in a conventional vehicle that travels with a drive force of an internal combustion engine, opening/closing of a changeover valve, a sealing valve, and a purge solenoid valve is controlled in operation of the internal combustion engine, a negative pressure is generated in a purge passage and a fuel tank by a negative pressure generated in an intake passage of the internal combustion engine, and a leak is determined by whether the negative pressure is held or not to detect presence or absence of a leak.
However, in a vehicle such as a plug-in hybrid vehicle that includes an internal combustion engine and also an electric motor, and travels mainly with a drive force of the electric motor, the internal combustion engine is rarely operated in order to improve fuel efficiency, and if a leak in the apparatus for suppressing fuel evaporative gas emission is to be detected in operation of the internal combustion engine, there are few opportunities for leak detection.
Thus, an apparatus for suppressing fuel evaporative gas emission provided in a vehicle with limited operation of an internal combustion engine includes a negative pressure pump that can reduce a pressure in the apparatus for suppressing fuel evaporative gas emission, and controls operation of the negative pressure pump, and opening/closing of a changeover valve, a sealing valve, and a purge solenoid valve during key-off of the vehicle to detect a leak in the apparatus for suppressing fuel evaporative gas emission (Japanese Patent No. 4151382).
In the apparatus for treating evaporative fuel of an internal combustion engine in Japanese Patent No. 4151382, a negative pressure pump unit is provided on an atmosphere open side of the canister.
Such a negative pressure pump unit includes a movable component in the negative pressure pump unit and has a gap, thereby preventing complete closing between an atmosphere side and a canister side.
Thus, for example, if a purge process is performed of discharging a fuel evaporative gas in the fuel tank or a fuel evaporative gas adsorbed to the canister to the intake passage of the internal combustion engine in operation of the internal combustion engine, and a negative pressure in the intake passage of the internal combustion engine is used to detect an abnormality such as a leak or an obstruction in the purge passage of the apparatus for treating evaporative fuel, the atmosphere flows into the canister from the atmosphere side of the negative pressure pump unit, which makes it difficult to accurately detect a leak or an obstruction in the purge passage. Also, the atmosphere flows into the canister from the atmosphere side of the negative pressure pump unit, and thus, unpreferably it takes time to generate a negative pressure necessary for detecting an abnormality such as a leak or an obstruction in the purge passage or the canister.